This invention relates to telecommunications terminal cards.
Telecommunications terminals connect subscriber lines, such as POTS (Plain Old Telephone Service) and ISDN (Integrated Services Digital Network) lines, to telecommunications exchanges and other telecommunications equipment. A terminal contains channel unit card slots that accept channel unit cards. Different types of channel unit cards service different types of subscriber lines (e.g. POTS or ISDN). Channel unit cards convert analog and digital signals from subscriber lines into formatted digital data signals. The terminal constructs a multiplexed signal from several channel unit cards""data signals for transmission to remote telecommunications equipment. The terminal also demultiplexes signals received from remote telecommunications equipment to deliver formatted digital data back to the channel unit cards. Channel unit cards convert the formatted digital data into a form suitable for transmission over subscriber lines.
Two telecommunications terminals can be connected xe2x80x9cback to backxe2x80x9d to form a digital loop carrier (DLC) network. A DLC network typically includes a remote terminal (RT) placed near a business or residence and a central office terminal (CT) placed in a central exchange connected to a telecommunications switch. The RT and CT communicate over a single line carrying multiplexed signals. This configuration connects subscribers to the telecommunications switch via the channel unit cards.
Channel unit cards handling subscriber lines must conform to telecommunications standards in the country in which the telecommunications terminal is deployed. While some countries use the same standards, for example, China, India, Korea, and Russia all require the same level of subscriber line impedance, many telecommunications standards differ. These standards govern transmission signal strength (e.g. Germany""s telephones generate 0 db signals while China""s telephones generate xe2x88x927 db signals), subscriber line impedance, and other telecommunications features. Additionally, each card provides transhybrid balance that cancels echoes in line. Transhybrid balance prevents the channel unit card from echoing a signal back to its sender.
DSC(trademark) Communications Corp. sells telecommunications terminals for use in different countries. DSC(trademark) manufactures different dedicated channel unit cards for the different telecommunications standards.
In general, in one aspect, a telecommunications card for use in a telecommunications terminal includes a subscriber line connection, a telecommunications terminal connection, and at least one programmable channel that carries signals between the subscriber line and the terminal. The channel can be programmed by configuration input to satisfy different telecommunications standards relating to subscriber lines.
Embodiments of the telecommunications card may include the following. The telecommunications standards may related to different countries. The telecommunications standards may include subscriber line impedance, gain, or transhybrid balance. The telecommunications card may be a POTS, RPOTS, CPOTS, ISDN, or other telecommunications card. The card channel may have circuit blocks that include selectable circuit paths that correspond to the different telecommunications standards and a standards selector that selects one of the paths based on configuration input. The circuit blocks may be xe2x80x9cplug-insxe2x80x9d where each block supports a set of telecommunications standards. The configuration input may be from sources that include dip switches or software messages. The circuit paths in the circuit blocks may terminate in relays controlled by the standards selector. The card channel may include a programmable codec that provides impedance and/or transhybrid balance. The card channel may also include an external network that, provides a base level of impedance. The external network may be interchangeable with other external networks that provide different base levels of impedance.
In general, in one aspect, a method of changing telecommunications standards for a telecommunications card includes receiving telecommunications standards selection information and modifying electrical characteristics of the telecommunications card based on the selection information.
Advantages may include one or more of the following.
A programmable telecommunications terminal card enables manufacturers to produce, stock, and ship a single card for a variety of countries with different telecommunications standards. Terminal administrators in these different countries can adapt a card to conform to the country""s standards with minimal hardware changes.
Other features and advantages will become apparent from the following description, including the drawings and the claims.